The use of cardiopulmonary bypass (CPB) and, especially, deep hypothermic cardiac arrest (DHCA) for the repair of congenital ehart defects results in alterations of cerebral blood flow and variable degrees of cerebral ischemia. When DHCA is used, there is an obligatory period of total cerebral ischemia. Neurodevelopmental dysfunction occurs in many children following repair of congenital heart defects, regardless of the support technique used. We hypothesize that specific differences in genetically coded mechanisms of neuronal maintenance and repair may result in increased susceptibility to post-operative neurologic dysfunction. The specific hypotheses to be tested are: 1: APOE genotype predicts the susceptibility of the central nervous system to short-term and long-term neurologic dysfunction associated with cardiac surgery in infants. 2: Patients with the APOE, 4 genotype have worse neurologic outcome following cardiac surgery. The aims of this study are to: 1) Conduct a single site, longitudinal, propsective, observational study of infants undergoing surgical repair of congenital heart disease and 2) Determine the association between APOE, 4 genotype with the incidence and severity of post-operative neurologic dysfunction at one year of age.